Hi, I don’t know any way to achieve this with “set leader pose component”, as indeed only main mesh Physical Asset is used.
Have you considered having separate animation blueprints for removable parts and just use “Copy Pose From Mesh”? Might be a little bit more expensive to handle multiple AnimBPs on one character, but should work well in your case.
In this article: Working with Modular Characters in Unreal Engine | Unreal Engine 5.5 Documentation | Epic Developer Community about in the middle you can find how to setup this copy pose thing.